1. Field of the Invention
The present invention relates to a display driving/controlling integrated circuit for supplying display data to a display unit such as a dot matrix display unit for effecting the 2-dimensional image display, and to a display system using the integrated circuit and, more particularly, to a display driving/controlling integrated circuit having a display memory for storing display data.
2. Description of the Related Art
When a display device such as a dot matrix type liquid crystal display device having a large number of display pixels is driven and controlled, an entire area of the display pixels is divided into a plurality of pixel areas and a display driving/controlling integrated circuit is provided for each divided pixel area.
FIG. 1 is a block diagram showing a display unit and a display driving/controlling integrated circuit. In FIG. 1, X indicates a number of pixels in a column direction of a display unit 90 and Y indicates a number of pixels in the a direction thereof. Further, Xa indicates a number of memory cells in a column direction of a display memory 92 disposed in a display driving/controlling integrated circuit 91 for controlling the display operation of the display unit 90 and Ya indicates a number of memory cells in a row direction thereof. For simplicity, in FIG. 1, only one display driving/controlling integrated circuit 91 is shown. If the total number of pixels in the display unit 90 is larger than the memory capacity of the display memory in the display driving/controlling integrated circuit 91, for example, if Y&gt;Ya and X&gt;Xa, the display unit 90 cannot be driven by use of only one display driving/controlling integrated circuit 91. Therefore, the entire area of the display pixels of 10 the display unit 90 is divided into a plurality of pixel areas and a plurality of display driving/controlling integrated circuits are used to drive the respective divided pixel areas. In the example of FIG. 1, that area of the display unit 90 which can be driven by one of the display driving/controlling integrated circuits 91 is a partial area A.sub.XY indicated by a hatched portion.
As shown in FIG. 2, when the display unit 90 is divided into four areas, four display driving/controlling integrated circuits 91a to 91d are provided to drive the respective four divided areas. The display driving/controlling integrated circuits 91a to 91d are supplied with data DB0 to DB7 from a CPU via a common data bus 93. That is, the four display driving/controlling integrated circuits 91a to 91d are allotted for the four divided areas of the display unit 90.
In order to make the type of integrated circuits uniform and lower the cost thereof, the same type of integrated circuits with the same arrangement, of input terminals for data DB0 to DB7 and output terminals S1 to S80 for driving signals are generally used as the four display driving/controlling integrated circuits 91a to 91d. Since the driving signals output from the output terminals S1 to S80 are supplied to segment lines (not shown) of the display unit 90 and the arrangement of the segment lines of the display unit 90 coincides with the arrangement of the output terminals of the integrated circuit in the two display driving/controlling integrated circuits 91a and 91b, which lie below the display unit 90 in FIG. 2, wirings between the display unit and the integrated circuits can be easily made. However, in FIG. 2, since the arrangement of the segment lines of the display unit 90 has an inverted relation with respect to the arrangement of the output terminals of the integrated circuits in the two display driving/controlling integrated circuits 91c and 91d, which lie above the display unit 90, special care must be taken when connecting wirings between the integrated circuits and the display unit 90.
For example, as shown in FIG. 3, the lower-side display driving/controlling integrated circuits 91a and 91b are mounted on the front surfaces of flexible wiring boards 95 and the wirings formed on the same surface of the flexible wiring boards 95 are connected to the segment lines of the display unit 90 as they are. However, the upper-side display driving/controlling integrated circuits 91c and 91d are mounted on the rear surfaces of respective flexible wiring boards 95, and in this case, the wirings formed on the rear surfaces of the flexible wiring boards must be re-arranged on the respective front surfaces thereof. At this time, it is required to form through hole connecting portions 95a in the flexible wiring board 95. However, if a necessary flexible wiring board 95 is prepared and the through hole connecting portions 95a are formed therein, the cost will become high. Further, in some cases, it is impossible to form an integrated circuit on the rear surface of the flexible wiring board 95.